You might want to have a huge garage bag with you at all times, just in case.

Some medical clinics/hospitals have valet parking, since... Well, sick and injured people might not want to walk nearly a mile for a ER or doctor visit.

As a general rule though, if you're impaired enough that you can't walk the length of a parking lot, you're probably not driving yourself around.

You'd be surprised. I'm generally talking about hospitals/clinics where the parking lots are separated from the medical building by several hundred yards, roads with heavy traffic, or ones that have a patient base with people who can technically walk the distance, but probably don't want to because of pain or other issues- orthopedic clinics, clinics that treat chemo patients, or patients with any disorder that causes pain associated with activity. There are a lot of chronically ill people that do wind up having to drive themself to appointments when, yes, they technically shouldn't be, but if they can't pay for a driving service and have been all but legally disowned by their family, they still have to get to the appointments.

In the end doesn't matter where he's going. If you shit your pants you don't make someone else sit in it. Period. If we are talking about a medical facility or even a hotel where the parking is valet only I'm sure 9/10 times they'll understand if you explain the accident and they'll show you where to put your car. Anywhere else you need to be turned away. It's a biohazard.

The ER at my local hospital has valet. Labor and Delivery has a separate valet as well. A friend of mine scarred a valet for life when he saw her give birth on the curb outside the hospital ;)

I think no shit is what OP wanted in the first place.

If he wasn't completely there, why is he allowed to drive?

It's not like the dmv gets a notification when someone's mind starts to slip.